This invention relates to a control signal generator circuit that controls the muting action and/or automatic frequency control action of a broadcast receiver such as an AM or FM receiver and to improved signal level indicators for use with such receivers.
In receivers of the above type, light-emitting indicators may be employed which indicate the level or strength of the received input signal. These indicators may comprise an integrated circuit, which may be called an LED array driver. The indicators typically include a reference voltage network and a plurality of comparators which sequentially light luminous elements such as LED's or lamps which are connected to the output terminals of the comparators. Thus, an additional luminous element is lighted with each predetermined increase in the receiver input signal. Typically, the light-emitting indicator is actuated by rectifying the intermediate frequency signal output (before amplitude limiting, if any) and applying the rectified output to the light-emitting indicator in order to sequentially light the luminous elements and thus indicate the receiver input level with a signal level indicator (the light-emitting indicator) instead of a signal level meter comprising a conventional analog meter.
Accordingly, it is a first object of this invention to provide a control signal generator circuit that controls automatic frequency control (AFC) action and/or muting action, for example, by using the light-emitting indicator employed as the signal level indicator in a broadcast receiver
It is a further object to light the luminous elements of the light-emitting indicator after controlling and stabilizing the AFC action and/or muting action with the control signals of the above control signal generator circuit.
Light-emitting indicators which have been heretofore available sequentially light the luminous elements at fixed input voltage steps of typically 200 mV. Further, some available indicators sequentially light the luminous elements over a predetermined fixed range of the input voltage.
Accordingly, it is a further object of this invention to provide a light-emitting indicator that can sequentially light the luminous elements over a variable input voltage range at variable steps with the variable range.
Other objects and advantages of this invention will be apparent from a reading of the following specification and claims taken with the drawing.